1. Field of the Invention
The present invention relates to a method and an apparatus for controlling an engine brake of a vehicle provided with a variable-speed V-belt drive.
2. Description of the Related Art
Vehicles provided with a variable-speed V-belt drive include all-terrain four-wheel vehicles. Such a variable-speed V-belt drive for a vehicle in capable of exercising what in called a belt clutch function which intercepts power transmission from a drive pulley to a belt extended between the drive pulley and a driven pulley, while the engine of the vehicle is stopped or in an idling operation.
The vehicle provided with such a variable-speed V-belt transmission capable of exercising a belt clutch function is unable to use engine brake when traveling down a slope because the engine is disconnected from the transmission when the engine speed decreases below a certain level.
A variable-speed V-belt drive disclosed in JP-A 165686/1999 for a vehicle is capable of automatically applying or taking off engine brake under a predetermined condition relating to, for examples traveling speed. The variable-speed V-belt drive is provided with a traveling-speed sensor, and an engine brake regulating lever for regulating the maximum V-groove width of the drive pulley. The engine brake regulating lever limits the reduction of the pitch diameter of the drive pulley when the traveling speed is above a certain level and the engine is idling so that the drive pulley and the belt are engaged effectively to make engine brake effective even while the engine is idling. This variable-speed V-belt drive is capable of applying or taking off engine brake according to acceleration or the like.
An engine brake control method mentioned in JP-A 165686/1999 moves the engine brake regulating lever between an engine brake applying position and an engine brake taking-off position to apply or take off engine brake by changing the maximum V-groove width of the drive pulley. The engine brake applying position for the engine brake regulating lever to apply engine brake is fixed. Therefore, the effect of engine bake changes with changes in the positional relation between the engine brake regulating lever and the movable sheave of the drive pulley with respect to the axial direction or the axial play of the V belt relative the movable sheave of the drive pulley after the variable-speed V-belt drive has been used for a certain service time.
The effect of engine brake decreases with the decrease of pressure applied to the V belt by the movable sheave of the drive pulley due to the wear of the V belt or the abrasion of the working surface of the engine brake regulating lever.
Accordingly, it is an object of the present invention to provide engine brake control method and apparatus capable of making engine brake effective or ineffective as the need arises, and of withholding the effect of engine brake from changing according to change in engine speed while engine brake is applied to maintain a fixed engine-braking effect. Moreover, it is another object to maintain a fixed engine-braking effect regardless of change in the pressure applied by the movable sheave of the drive pulley to the V belt due to the wear of the V belt and the abrasion of the associated parts.
According to the first aspect of the present invention, an engine brake control method for a vehicle provided with a variable-speed V-belt drive including a drive pulley having a movable sheave, a driven pulley, and a V belt extended between the drive pulley and the driven pulley, comprises: detecting a position of an engine brake regulating member by a detector, the engine brake regulating member listing an extent of an outward axial movement of the movable sheave of the drive pulley so an to regulate a maximum V-groove width of the drive pulley; and controlling a position of the engine brake regulating member by a controller based on a position signal sent from the detector to the controller, the controller operating an actuator to move the engine brake regulating member so that the engine brake regulating member is located at a desired position relative to the movable sheave of the drive pulley.
According to the present invention, when engine brake is applied to the vehicle, the dislocation of the engine brake regulating member from a correct position can be automatically corrected to maintain the effect of engine brake constant.
Preferably, the detecting step detects a reference position of the engine brake regulating member where the engine brake regulating member is located when the engine brake regulating member comes into contact with the movable sheave. The controlling step controls a position of the engine brake regulating member using the reference position detected in the detecting step an a reference.
Thus, even after the variable-speed V-belt drive has been used for a long service time, the maximum V-groove width of the drive pulley can be easily adjusted without requiring manual adjustment according to the existing position and dimensions of the movable sheave of the drive pulley.
Preferably, the detecting step detects a reference position of the engine brake regulating member where the engine brake regulating member is located when the movable sheave, which is pressed inward by the engine brake regulating member, comes into contact with the V belt. The controlling step controls a position of the engine brake regulating member using the reference position detected in the detecting step as a reference.
Thus, the position of the movable sheave of the drive pulley for the maximum V-groove width of the drive pulley can be determined regardless of clearance between the movable sheave of the drive pulley and the V belt, which further enhances the effect on maintaining the effect of engine brake constant.
Preferably, the detecting step is executed when a main switch of the vehicle is opened.
Thus, the working position of the engine brake regulating member can be automatically corrected when the operation of the vehicle is stopped so that the engine brake regulating member can be always held at a proper position to prevent the reduction of the effect of engine brake. Since the position of the engine brake regulating member is not detected when the main switch is closed, the vehicle is able to start without any time lag due to the detection of the position of the engine brake regulating member after the main switch has been closed.
Preferably, the actuator is electrically driven.
According to the second aspect of the present invention, an engine brake control apparatus for a vehicle provided with a variable-speed V-belt drive including a drive pulley having a movable sheave, a driven pulley, and a V belt extended between the drive pulley and the driven pulley, comprises: an engine brake regulating member of limiting an extent of an outward axial movement of the movable sheave of the drive pulley so as to regulate a maximum V-groove width of the drive pulley; a detector of detecting a position of the engine brake regulating member; an actuator of moving the engine brake regulating member; and a controller of controlling a position of the engine brake regulating member by operating the actuator based on a position signal sent from the detector so that the engine brake regulating member is located at a desired position relative to the movable sheave of the drive pulley.
According to the present invention, when engine brake is applied to the vehicle, the dislocation of the engine brake regulating member from a correct position can be automatically corrected to maintain the effect of engine brake constant.
Preferably, the detector detects a reference position of the engine brake regulating member where the engine brake regulating member is located when the engine brake regulating member comes into contact with the movable sheave. The controller controls a position of the engine brake regulating member using the reference position detected by the detector as a reference.
Thus, even after the variable-speed V-belt drive has been used for a long service time, the maximum V-groove width of the drive pulley can be easily adjusted without requiring manual adjustment according to the existing position and dimensions of the movable sheave of the drive pulley.
Preferably, the detector detects a reference position of the engine brake regulating member where the engine brake regulating member is located when the movable sheave, which is pressed inward by the engine brake regulating member, comes into contact with the V belt. The controller controls a position of the engine brake regulating member using the reference position detected by the detector as a reference.
Thus, the position of the movable sheave of the drive pulley for the maximum V-groove width of the drive pulley can be determined regardless of clearance between the movable sheave of the drive pulley and the V belt, which further enhances the effect on maintaining the effect of engine brake constant.
Preferably, the detector detects the position of the engine brake regulating member when a main switch of the vehicle is opened.
Thus, the working position of the engine brake regulating member can be automatically corrected when the operation of the vehicle is stopped so that the engine brake regulating member can be always held at a proper position to prevent the reduction of the effect of engine brake. Since the position of the engine brake regulating member is not detected when the main switch is closed, the vehicle is able to start without any time lag due to the detection of the position of the engine brake regulating member after the main switch has been closed.
Preferably, the actuator is electrically driven.